Electrical machine with air-cooled control chip

ABSTRACT

In an electrical machine, in particular a generator for a motor vehicle, having a housing ( 2 ), a rotor ( 6 ), supported rotatably in the housing ( 2 ) about a pivot axis ( 5 ), at least one fan wheel ( 20 ), connected to the rotor ( 6 ), for generating a cooling air flow ( 22, 22′, 22 ″) from at least one intake opening ( 37; 37′; 37 ″) disposed in the housing ( 2 ) to at least one outlet opening ( 24 ) disposed in the housing ( 2 ), and at least one regulator chip ( 31 ), disposed on a chip holder ( 30 ), for regulating the current generation, it is provided that the chip holder ( 30 ) is disposed such that it is bathed at least in part directly by the cooling air flow ( 22, 22′, 22 ″). As a result of this arrangement, it is attained that a very high heat transfer coefficient is present, because of the high flow speed of the cooling air flow ( 22, 22′, 22 ″).

BACKGROUND OF THE INVENTION

The invention relates generally to an electrical machine, in particulara generator for a motor vehicle.

From U.S. Pat. No. 5,907,203, a generator for a motor vehicle is knownin which a voltage regulator is connected electrically to the slip ringassembly. The generator has a cooling conduit, which extends past avoltage regulator. The voltage regulator includes a housing, a printedcircuit board, and a regulator chip, which are mounted on a fasteningplate. The fastening plate of the regulator directly adjoins the coolingair conduit. The cooling air conduit is created by a spacer element,which spaces the fastening plate apart from the generator housing. Adisadvantage of this embodiment is that the printed circuit board withthe regulator chip is mounted on an additional fastening plate. The heattransfer to the aspirated cooling air is restricted by the fasteningplate on which the regulator chip is mounted. Accordingly, the coolingair flow does not come into direct contact with the printed circuitboard or the regulator chip. Moreover, because of the spacer element, alarger installation space is needed, which adversely affects the size ofthe generator. Moreover, higher production costs result from theadditional costs for material and assembly.

It is accordingly the object of the invention to create an electricalmachine, in particular a generator, with improved cooling of theregulator.

The nucleus of the invention is that the chip holder is disposed suchthat it is bathed at least in part directly by the cooling air flow. Inaccordance with further features of the invention, it is provedadvantageous to dispose the chip holder at a point where the speed ofthe cooling air flow is especially high, because the heat transfer isquite pronounced at that point.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in further detail below in terms of preferredexemplary embodiments in conjunction with the drawing. Shown are:

FIG. 1, a cross section through a generator with a claw pole rotor in afirst embodiment;

FIG. 2, an enlarged detail of the view of FIG. 1 of the generatorregulator and slip ring bearing plate, in a first embodiment;

FIG. 3, a cross section as in FIG. 2, through a second embodiment; and

FIG. 4, a cross section as in FIG. 3, through a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment of the invention will be described below, referringto FIGS. 1 and 2. An electrical machine, in this exemplary embodiment agenerator 1, for motor vehicles, in a diecast housing 2 comprising twohousing halves 3 and 4, has a claw pole rotor 6, which is supportedrotatably about a pivot axis 5 and has a shaft 7. Outside housing half4, a pulley 10 is mounted, secured by a nut 11, on the end of the rotorshaft 7 in order to drive the rotor 6. A slip ring assembly 12 isprovided on the other end of the rotor shaft 7. The slip ring assembly12 includes slip rings on the rotor shaft 7. The slip rings cooperatewith carbon brushes in a known manner. The supporting of the rotor shaft7 is effected by means of two ball bearings 8 and 9. The housing half 4is embodied as a bearing plate for the ball bearing 8 on the drive side,and the ball bearing 8 takes on the function of the fixed bearing. Thehousing half 3 is embodied as a slip ring bearing plate 25 for the ballbearing 9 on the slip ring side; the ball bearing 9 is embodied smallerand in the form of a loose bearing. The two housing halves 3 and 4,joined together by screws 13, fix a central stator lamination packet 14,which in a known manner receives a three-phase stator winding 15 forgenerating a rotary current. The rotor shaft 7, in its middle region ona magnetically conductive annular core 16, carries a rotor winding 17,which is equivalent to an exciter winding. Claw pole jacks 18 thataxially directly adjoin the annular core 18 and rotor winding 17 at thefront and back are secured to the rotor shaft 7. The claw pole prongs 19of the claw pole jacks 18 engage on another with spacing to form analternating field. One fan wheel 20 is mounted on each of the outer faceends of the claw pole jacks 18 on the rotor shaft 7; because of therotation of the rotor shaft 7, it axially aspirates ambient air throughslits, not shown, in the housing half 3 and feeds it radially, past thewinding head 23, toward the slip ring, of the stator winding 15 to theoutside through radial outlet openings 24. The fan wheel 20 disposed onthe drive-side face end of the claw pole jack 15 likewise aspiratesambient air axially through slits, not shown, in the housing half 4 andblows them through outlet openings to the outside, past the frontwinding head of the stator winding 15. The generator 1 is accordinglyair-cooled. The supply of current to the rotor winding 17 is effectedthrough the slip ring assembly 12, of which one slip ring each iselectrically connected to one end of the rotor winding 17. On the sideof the fan wheel 20 toward the slip ring and remote from the claw polejack 18, the slip ring bearing plate 25 is spaced apart somewhat, and aregulator 28 is integrated with it in a recess 26 in the region of thefan blade 27. The regulator 28 regulates the direct current flowing inthe rotor winding 17 to suit the demands of the on-board electricalsystem of a motor vehicle.

In a regulator housing 29, the regulator 28 includes a chip holder 30 ofrectangular cross section, with a smaller regulator chip 31 secureddirectly on it and likewise having a rectangular cross section.Alternatively, the regulator chip 31 can be secured by adhesive bondingor soldering. The chip holder 30 of the regulator 28 is surrounded by alateral thermal insulation 33. The regulator housing 29 is closed by aprotective cap 34. A plug unit 35 with a connection 36 is disposed inthe regulator housing 29, on the outer face end of the housing half 3.

In the generator 1, the chip holder 30 is located in the recess 26 inthe slip ring bearing plate 25, and with a plastic layer that forms thethermal insulation 33, the chip holder 30 is thermally insulated fromthe slip ring bearing plate 25. Heating of the regulator chip 31 by theslip ring bearing plate 25 is prevented by this insulation 33. Theunderside 21 of the chip holder 30, oriented toward the fan wheel 20 onthe side toward the slip ring, protrudes somewhat from the recess 26into the interior of the generator 1. In the slip ring bearing plate 25,there is a separate intake opening 37 for a cooling air flow 22 locatedbetween the ship holder 30, mounted in the recess 26, and the rotorshaft 7.

The cooling of the regulator chip 31 is accomplished in that the coolingair flow 22 is aspirated through the intake opening 37 by means of thefan wheel 20 toward the slip ring and is then blown inward, along theslip ring bearing plate 25, to the outlet openings 24. In the process,the cooling air flow 22 passes the underside 21 of the chip holder 30that has become heated by the regulator chip 31. For this reason, thechip holder 30 comprises a highly heat-conductive material. Because ofits thermal insulation 33, excessive heating of the regulator 28 fromthe component temperature of the slip ring bearing plate 25 isprevented. The underside 21 of the chip holder 30 is placed directly onthe fan blades 27, because very high flow speeds and hence high heattransfer coefficients of the cooling air flow 22 occur there. Since thewaste heat is dissipated there especially well, efficient cooling of theregulator 28 is achieved. Thus the generator 1 can be used forapplications that involve relatively high ambient temperatures.

Cooling of the regulator 28 without a separate cooling body is possiblebecause of this arrangement, resulting in a very economical regulator28. To enhance the cooling effect still more, the possibility alsoexists of providing cooling fins on the chip holder 30, to increase thesurface area. In addition, the regulator chip 31 is secured to aleadframe or a bus, which extend directly within the cooling air flow22. In this connection, a leadframe is understood to mean busesoriginally communication with one another through a frame. The coolingof the regulator chip 31 is further improved because of thisarrangement.

A second embodiment of the invention will now be described, inconjunction with FIG. 3. Identical parts are assigned the same referencenumerals as in the first exemplary embodiment, whose description ishereby referred to. Structurally different but functionally identicalparts are assigned the same reference numerals, with a prime.

This exemplary embodiment differs in that the regulator 28 is secured ata distance from the slip ring bearing plate 25′ by means of two spacers38; it can also be secured with more than two spacers 38. The chipholder 30 of the regulator 28 is accordingly disposed in front of theintake opening 37′ positioned in the region of the fan wheel blade 27;that is, it is positioned outside the housing half 3. The cooling airflow 22′ is aspirated through the intake opening 37′ by the fan wheel 20toward the slip ring and is then blown out radially through the outletopenings 24. In this exemplary embodiment, the recess 26 forms theintake opening 37′.

The cooling is achieved because the cooling air flow 22′ first flowspast the chip holder 30 before being carried through the intake opening37′ to the fan wheel 20. The chip holder 30 is capable of dissipatingthe waste heat from its underside 21 and laterally to the cooling air22′. The surface area of the chip holder 30 bathed by the flow isincreased in size, in comparison with the first embodiment, so thatbetter cooling is achieved. This embodiment is preferable above allwhenever the cooling air flow 22′ through the fan wheel 20 toward theslip ring has already been heated excessively, and adequate cooling ofthe regulator 28 can no longer be accomplished. Thus the chip holder 30is disposed at a point where the speed of the cooling air flow 22′,because of the immediate vicinity of the face-end fan wheel 20, isespecially high, making efficient cooling attainable.

A third embodiment of the invention will now be described, inconjunction with FIG. 4. Identical parts are once again assigned thesame reference numerals as in the first exemplary embodiment, whosedescription is hereby referred to. Structurally different butfunctionally identical parts are therefore assigned the same referencenumerals, with a double prime. The regulator 28 is once again placedwith its chip holder 30 in a recess 26 directly on the fan wheel blades27. The underside 21 of the chip holder 30 protrudes somewhat into theinterior of the generator 1. The intake opening 37″ is disposed in theslip ring bearing plate 25″ directly on the side, toward the rotor shaft7, of the chip holder 30. The thermal insulation 33″ is embodied alongthe intake opening 37″ only over a portion 39 of the side 41 of the chipholder 30, thus creating a face 40 without the thermal insulation 33″.

In this embodiment, the cooling function is accomplished in that thecooling air flow 22″, which is not heated, is aspirated axially throughthe intake opening 37″ by means of the fan wheel 20 on the side towardthe slip ring bearing and is blown out radially through the outletopenings 24. Since the intake opening 37″ is positioned directly on thechip holder 30, waste heat from the chip holder 30 is already dissipatedin the intake opening 37″. In addition, the underside 21, extendingparallel to the fan wheel 20, is likewise bathed by the cooling air flow22″. Since the thermal insulation 33″ on the side 41 is embodied inshortened form, and the cooling air flow 22″ meets the face 40 directlyat the chip holder 30, the heat transfer in this region is furtherreinforced. Thus the heat dissipation in this embodiment takes placeboth at the non-insulated face 40 and on the underside 21 of the chipholder 30 by means of the cooling air flow 22″. Once again, the chipholder 30 is disposed at a point where the speed of the cooling air flow22″ is especially high. The longitudinal dimensions of the generator 1in this embodiment are shortened by the length of the spacers 38,compared to the embodiment described in FIG. 2. In comparison to theembodiment shown in FIG. 1, the heat dissipation is improved because ofthe larger bathed surface area. The cooling of the regulator 28 iseffected by partly heated and not heated air of the cooling air flow22″.

1. An electrical machine in the form of a generator for a motor vehicle,comprising: a housing (2); a rotor (6), supported rotatably in thehousing (2) about a pivot axis (5); at least one fan (20), connected tothe rotor (6), for generating a cooling air flow (22″) from at least oneintake opening (37″) disposed in the housing (2) to at least one outletopening (24) disposed in the housing (2); and at least one regulatorchip (31), directly disposed on a chip holder (30), for regulating thecurrent generation, wherein the chip holder (30) is disposed such thatit is bathed at least in part directly by the cooling air flow (22″), isreceived in a recess (26) in the housing (2), and is thermally insulatedby a thermal insulation (33″) from the housing (2), wherein the at leastone intake opening (37″) in the housing (2) disposed immediatelyadjacent the chip holder (30) in the housing (2), so that waste heatfrom the chip holder (30) is already dissipated in the intake opening(37″).
 2. The electrical machine of claim 1, wherein the chip holder(30) is a leadframe or a bus.
 3. The electrical machine of claim 1,wherein the chip holder (30) is disposed at a point where the speed ofthe cooling air flow (22″) is especially high.
 4. The electrical machineof claim 1, wherein the chip holder (30) comprises a highlyheat-conductive material.
 5. An electrical machine in the form of agenerator for a motor vehicle, comprising: a housing (2); a rotor (6)supported rotatably in the housing (2) about a pivot axis (5); at leastone fan (20) connected to the rotor (6) for generating a cooling airflow (22) from at least one intake opening (37) disposed in the housing(2) to at least one outlet opening (24) disposed in the housing (2); andat least one regulator chip (31) directly disposed on a chip holder (30)for regulating current generation, wherein the chip holder (30) isdisposed such that the chip holder is bathed at least in part directlyby the cooling air flow (22), is received in a recess (28) in thehousing (2), and is thermally insulated by a thermal insulation (33)from the housing (2), wherein the at least one intake opening (37) inthe housing 92) is spaced apart from the chip holder (30) in the housing(2).
 6. An electrical machine in the form of a generator for a motorvehicle, comprising a housing (2); a rotor (6), supported rotatably inthe housing (2) about a pivot axis (5); at least one fan (20), connectedto the rotor (6), for generating a cooling air flow (22″) from at leastone intake opening (37″) disposed in the housing (2) to at least oneoutlet opening (24) disposed in the housing (2); and at least oneregulator chip (31), directly disposed on a chip holder (30), forregulating the current generation, wherein the chip holder (30) isconfigured integrally, is disposed such that it is bathed at least inpart directly by the cooling air flow (22″), is received in a recess(26) in the housing (2), and is thermally insulated by a thermalinsulation (33″) from the housing (2), wherein the at least one intakeopening (37) in the housing (2) is disposed immediately adjacent thechip holder (30) in the housing (2), so that waste heat from the chipholder (30) is already dissipated in the intake opening (37″).
 7. Anelectrical machine in the form of a generator for a motor vehicle,comprising a housing (2); a rotor (6), supported rotatably in thehousing (2) about a pivot axis (5); at least one fan (20), connected tothe rotor (6), for generating a cooling air flow (22) from at least oneintake opening (37) disposed in the housing (2) to at least one outletopening (24) disposed in the housing (2); and at least one regulatorchip (31), directly disposed on a chip holder (30), for regulating thecurrent generation, wherein the chip holder (30) is configuredintegrally, is disposed such that it is bathed at least in part directlyby the cooling air flow (22), is received in a recess (26) in thehousing (2), and is thermally insulated by a thermal insulation (33)from the housing (2), wherein the at least one intake opening (37) inthe housing (2) is spaced apart from the chip holder (30) in the housing(2).